1. Field of the Invention
The present invention relates to a technology for recognizing the shape of a road on which a vehicle is traveling.
2. Description of the Related Art
Conventionally, a road shape recognition apparatus is known that recognizes the shape of a road on which a vehicle is traveling, based on the position of a roadside object (refer to, for example, JP-B-3417375, JP-A-2012-242934, and JP-A-2012-242935). For detecting the roadside object, a transmission wave, such as an optical wave or a millimeter-wave is radiated over a predetermined angle ahead of or to the side of the vehicle and a reflection wave thereof is received.
In the conventional road shape recognition apparatus, in a situation in which the position of a roadside object can be continuously detected, such as when the roadside object is a traffic strip composed of a structure such as a guardrail or shrubbery, a fence, or a block wall, the road shape can be recognized. However, in a situation in which the position of a roadside object is discontinuously detected, such as when the roadside object is a roadside tree or a building, a problem occurs in that recognition accuracy significantly decreases. In addition, in a situation in which a roadside object is not present to begin with, such as when the vehicle is traveling on an embankment, the road shape cannot be recognized.
Therefore, road shape recognition using a known white-line detection technology that uses a camera can be considered. However, in a situation in which the white line is faded, for example, recognition accuracy significantly decreases. In a situation in which a white line is not present to begin with, the road shape cannot be recognized.